In various molding processes, e.g. in the production of synthetic resin or elastomeric articles, the molded product is left with material which must subsequently be removed and may result from sprues for feed passages for the molded material, waste which arises because the molded parts do not close with precision against one another, or the like, such wastes being referred to as burrs or flashings.
For the purposes of the present application the deflashing or the removal of such waste will be described as a flashing removal regardless of the nature of the excess which must be removed, the type of article from which the flashing is to be removed, and whether the material is generally termed flashing or a burr or has some other designation for a particular article and its method of fabrication.
Thus the present description applies to articles which are injection molded, die cast, die pressed or even extruded and, indeed, regardless of the particular fabrication technique.
The flashing generally appears as a web projecting from a surface or a thin strip of somewhat irregular form projecting from an edge of the article or workpiece and should be removed as close to the edge or surface as possible, i.e. at the foot or base of the flashing.
In general terms, therefore, the invention is concerned with the removal of all excess material which can be defined as material projecting from the ideal configuration of the article.
It is known to deburr or deflash relatively large molded articles of the type described manually and by various techniques generally involving cutting away of the flashing. Manual flashing removal is extremely expensive. For the removal of such waste by machine, it has been proposed to cool the object to be deflashed to thereby embrittle the flashing and to then break it away.
It is also known to remove rubber flashings or wastes of a filigree pattern in a molded state from grooves, holes and the like with the aid of sand or shot blasting. In the latter case, the article to be deflashed can be tumbled in a container and cooled with a cryogenic medium and then subjected to sand blasting or steel shot blasting.
In another process for the deflashing of articles by mechanical means, the articles are tumbled in the presence of an aggregate or impact medium and the particles of the impact medium gradually break away by random impact against the flashing, the waste material. This process does not provide the desired deflashing quality.
Perforated drums which operate with blast systems of the type described can also be used and while edge wastes can be easily removed in such systems, there is always a danger that the articles will be damaged.
When a shot or sand blasting technique is used for economical reasons it is essential to separate the blast medium, i.e., shot or sand, from the residues removed from the article and to recycle the blast medium. For this purpose, it is necessary to operate in a closed system and this requirement, of course, increases the cost of operation as well as the cost of the apparatus required for carrying out the method.